The sensing of bacteria is a key tool for combating water contamination, food poisoning and infectious disease, as well for protection against biological warfare agents. In our proposed research, we will develop an array-based sensor for bacteria based on electrostatic conjugates formed from cationic gold nanoparticles and highly fluorescent anionic conjugated polymers. In these conjugates fluorescence emission from the polymer is quenched via energy transfer to the nanoparticle. In preliminary studies, we have demonstrated that the differential response observed with a set of three particles allowed identification of 13 bacteria featuring Gram negative and positive species, as well as differentiation between three different strains of E. coli. In our proposed research, we will focus on increasing the scope and sensitivity of this method, as well as test its applicability in complex media including serum and urine. Aim 1: Rotello will synthesize nanoparticles featuring a wide variety of headgroup functionality for targeting bacterial surfaces. The tailorable interfaces of these particles will provide the selectivity required for the creation of sensing systems. Concurrently, Bunz will synthesize conjugated polymer (CP) polyelectrolytes featuring complementary charges. These CPs will be customized in regards to affinity and fluorescent behaviour, providing multiplex sensing capabilities. Aim 2: Rotello and Bunz will develop prototype sensors for bacteria. Preliminary studies will explore the limits of detection for general bacteria sensing. Further studies will explore the degree of selectivity obtainable using MMPC-based receptors, with the ultimate goal the identification and quantification of pathogenic bacteria using chemometric protocols developed by Voigtman. Relevance: The goal of this research is to provide sensors that can rapidly identify bacteria (<5 min). These sensors should have applicability in testing of drinking water and identification of bioterrorism agents. We will also explore sensing in complex media including serum and urine, providing potential diagnostics for infections bacterial infections. Rationale for R21 Mechanism: The major innovation of this proposal is the creation of a highly sensitive displacement sensor for bacteria. The approach uses multivalent interactions between polymers and nanoparticles, coupled with the ability to engineer the surface properties of nanoparticles to provide controlled interactions with biological systems. The R21 grant will provide proof of concept studies demonstrating the utility of these sensors. If successful, these results will provide the foundation for sensors with applications in biomedical diagnostics that will be pursued under the R01 mechanism. PUBLIC HEALTH RELEVANCE: In our proposed research we will create sensors for the detection and identification of bacteria. These sensors will be useful for detecting bacteria in water supplies, providing protection against contamination from environmental or bioterrorist sources. These sensors will also be applied to blood models (serum), providing potential diagnostics for bacterial infections.